The steroid hormone cortisol is a key regulator of many physiological processes. However, an excess of cortisol, as occurs in Cushing's Disease, provokes severe metabolic abnormalities including: type 2 diabetes, cardiovascular disease, obesity, and osteoporosis. Many patients with these diseases, however, do not show significant increases in plasma cortisol levels. In addition to plasma cortisol, individual tissues can regulate their glucocorticoid tone via the in situ conversion of inactive cortisone to the active hormone cortisol. Indeed, the normally high plasma concentration of cortisone provides a ready supply of precursor for conversion to cortisol via the intracellular enzyme 11-beta-hydroxysteroid dehydrogenase type I (11beta-HSD1).
11beta-HSD1 is a member of the short chain dehydrogenase superfamily of enzymes. By catalyzing the conversion of cortisone to cortisol, 11beta-HSD1 controls the intracellular glucocorticoid tone according to its expression and activity levels. In this manner, 11beta-HSD1 can determine the overall metabolic status of the organ. 11beta-HSD1 is expressed at high levels in the liver and at lower levels in many metabolically active tissues including the adipose, the CNS, the pancreas, and the pituitary. Taking the example of the liver, it is predicted that high levels of 11beta-HSD1 activity will stimulate gluconeogenesis and overall glucose output. Conversely, reduction of 11beta-HSD1 activity will down regulate gluconeogenesis resulting in lower plasma glucose levels.
Various studies have been conducted that support this hypothesis. For example, transgenic mice expressing 2× the normal level of 11beta-HSD1 in only the adipose tissue show abdominal obesity, hyperglycemia, and insulin resistance. (Masuzaki, H. et al., “A Transgenic Model of Visceral Obesity and the Metabolic Syndrome”, Science, 294:2166-2170 (2001). Conversely, when the 11beta-HSD1 gene is ablated by homologous recombination, the resulting mice are resistant to diet induced obesity and the accompanying dysregulation of glucose metabolism (Morton, N. M. et al., “Novel Adipose Tissue-Mediated Resistance to Diet-induced Visceral Obesity in 11β-Hydroxysteroid Dehydrogenase Type 1-Deficient Mice”, Diabetes, 53:931-938 (2004). In addition, treatment of genetic mouse models of obesity and diabetes (ob/ob, db/db and KKAy mice) with a specific inhibitor of 11beta-HSD1 causes a decrease in glucose output from the liver and an overall increase in insulin sensitivity (Alberts, P. et al., “Selective Inhibition of 11β-Hydroxysteroid Dehydrogenase Type I Improves Hepatic Insulting Sensitivity in Hyperglycemic Mice Strains”, Endocrinology, 144:4755-4762 (2003)). Furthermore, inhibitors of 11beta-HSD1 have been shown to be effective in treating metabolic syndrome and atherosclerosis in high fat fed mice (Hermanowski-Vosatka et al., J. Exp. Med., 202(4):517-527 (2002)). Based in part on these studies, it is believed that local control of cortisol levels is important in metabolic diseases in these model systems. In addition, the results of these studies also suggest that inhibition of 11beta-HSD1 will be a viable strategy for treating metabolic diseases such as type 2 diabetes, obesity, and the metabolic syndrome.
Lending further support to this idea are the results of a series of preliminary clinical studies. For example, several reports have shown that adipose tissue from obese individuals has elevated levels of 11beta-HSD1 activity. In addition, studies with carbenoxolone, a natural product derived from licorice that inhibits both 11beta-HSD1 and 11beta-HSD2 (converts cortisol to cortisone in kidney) have shown promising results. A seven day, double blind, placebo controlled, cross over study with carbenoxolone in mildly overweight individuals with type 2 diabetes showed that patients treated with the inhibitor, but not the placebo group, displayed a decrease in hepatic glucose production (Andrews, R. C. et al., J. Clin. Endocrinol. Metab., 88:285-291 (2003)). This observation is consistent with the inhibition of 11beta-HSD1 in the liver. The results of these preclinical and early clinical studies strongly support the concept that treatment with a potent and selective inhibitor of 11beta-HSD1 will be an efficacious therapy in patients afflicted with type 2 diabetes, obesity, and the metabolic syndrome.
Accordingly, compounds that activate 11beta-HSD1 could demonstrate a wide range of utilities in treating diabetes and related conditions, microvascular complications associated with diabetes, the macrovascular complications associated with diabetes, cardiovascular diseases, Metabolic Syndrome and its component conditions, inflammatory diseases and other maladies. PCT Publication Nos. WO 2006/135667 A1, WO 2006/135795 A1, WO 2008/024892 A1, WO 2008/130951 A1, WO 2009/045753 A1 (incorporated herein by reference and assigned to present applicant) and WO 2009/102761 A1, disclose compounds that activate 11beta-HSD1. The references also disclose various processes to prepare these compounds.
It is desirable to find new compounds with improved pharmacological characteristics compared with known 11beta-HSD1 activators. For example, it is desirable to find new compounds with improved 11beta-HSD1 activity and selectivity for 11beta-HSD1 versus other dehydrogenase receptors (i.e., 11beta-HSD2 receptor). It is also desirable to find compounds with advantageous and improved characteristics in one or more of the following categories:
(a) pharmaceutical properties (i.e., solubility, permeability, amenability to sustained release formulations);
(b) dosage requirements (e.g., lower dosages and/or once-daily dosing);
(c) factors which decrease blood concentration peak-to-trough characteristics (i.e., clearance and/or volume of distribution);
(d) factors that increase the concentration of active drug at the receptor (i.e., protein binding, volume of distribution);
(e) factors that decrease the liability for clinical drug-drug interactions (cytochrome P450 enzyme inhibition or induction, such as CYP 2D6 inhibition, see Dresser, G. K. et al., Clin. Pharmacokinet., 38:41-57 (2000), which is hereby incorporated by reference); and
(f) factors that decrease the potential for adverse side-effects (e.g., pharmacological selectivity beyond the intracellular enzyme 11-beta-hydroxysteroid dehydrogenase type I, potential chemical or metabolic reactivity, limited CNS penetration, ion-channel selectivity). It is especially desirable to find compounds having a desirable combination of the aforementioned pharmacological characteristics.